1. Field of the Invention
The present invention relates to a position detection sensor unit and a position detection apparatus for detecting a position of a pointer such as a finger or a position pointer.
2. Description of the Related Art
A position detection apparatus for detecting a position pointed to by a pointer such as a finger or a pen is known. As a position detection method used for the position detection apparatus, various methods are available such as a resistive film method, an electromagnetic induction method, a capacitance method and so forth.
FIG. 8 shows a configuration of an example of a sensor section of a position detection apparatus of the capacitance type. Referring to FIG. 8, the position detection apparatus is of the capacitance type of a so-called cross point capacitance type, which is developed from the capacitance type of a projection type. The sensor section of the position detection apparatus of the cross point capacitance type is configured such that it includes a plurality of upper electrodes Ex extending, for example, in a Y-axis direction or longitudinal direction of a pointing inputting face and a plurality of lower electrodes Ey extending in an X-axis direction or lateral direction. The upper electrodes Ex and the lower electrodes Ey are juxtaposed in a predetermined spaced relationship in the X-axis direction and the Y-axis direction, respectively, and perpendicularly cross each other while they are arrayed with a small gap interposed therebetween. In this instance, a predetermined fixed capacitor Co is formed at an overlapping portion, that is, at a cross point between each upper electrode Ex and each lower electrode Ey.
When a pointer 1000, such as a position pointer held by the user or a finger of the user, approaches or comes in contact with a position on the pointing inputting face, a capacitor Cf is formed between the pointer 1000 and the electrodes Ex and Ey at that position. The pointer 1000 is connected to the ground through the human body, that is, through a capacitor Cg. As a result, due to the capacitors Cf and Cg, the amount of movement of the charge between the upper electrode Ex and the lower electrode Ey at the position pointed to by the pointer 1000 varies. In the position detection apparatus of the cross point capacitance type, the position pointed to by the pointer 1000 on the pointing inputting face can be specified by detecting the variation of the amount of movement of the charge.
This variation of the amount of movement of the charge is detected by a signal processing circuit 1001. The signal processing circuit 1001 supplies a predetermined transmission signal to a lower electrode Ey used, for example, as a transmission electrode and receives a reception signal from an upper electrode Ex used as a reception electrode. The signal processing circuit 1001 detects a current variation of the reception signal to detect a variation of the amount of movement of the charge. The signal processing circuit 1001 switches between the transmission electrodes to supply a transmission signal to, and sequentially carries out a detection process of the current variation of the reception signal from the reception electrodes, to thereby detect the position of a pointer.
Not only in a sensor section of the cross point capacitance type as described above but also in any sensor section of the capacitance type, for the purpose of detecting the variation of the amount of movement of charge as described above, the distance between the pointer and the detection electrodes should be made as small as possible. Therefore, Japanese Patent Laid-Open No. 2011-64658 (hereinafter referred to Patent Document 1) describes a sensor section of the capacitance type, which is affixed to the surface or front face of the housing of the position detection apparatus. The sensor section is connected to the signal processing circuit in the inside of the housing via a cable of flexible material (a flexible cable) extending through an opening perforated in the housing.
FIGS. 9A to 9C show a structure of a position detection apparatus 100 including a sensor of the capacitance type as disclosed in Patent Document 1. FIG. 9A is a view of the position detection apparatus 100 as viewed from the face side, which accepts a pointing input of a pointer, and FIG. 9B is an enlarged sectional view taken along line A-A of FIG. 9A.
A housing 110 of the position detection apparatus 100 includes an upper case 1101 and a lower case 1102. A sensor section 120 of the capacitance type, hereinafter referred to as a position detection sensor unit 120, is affixed to the upper case 1101 of the housing 110. A signal processing circuit 130 for the position detection sensor unit 120 is provided in a space between the upper case 1101 and the lower case 1102 of the housing 110. The position detection sensor unit 120 and the signal processing circuit 130 are connected to each other via a through-hole 1104 provided in the upper case 1101.
The position detection sensor unit 120 is configured such that a sensor substrate 1202 formed of a flexible substrate is affixed by adhesive to the rear face side of a sheet member 1201 made of insulating material. The sheet member 1201 functions as a position pointing operation member, and the front face side thereof serves as a surface to which pointing input operation directed to a position is carried out by a pointer. On the flexible substrate of the sensor substrate 1202, a sensor including a conductor pattern of the electrodes Ex and Ey described hereinabove is formed.
From the position detection sensor unit 120, a flexible cable 1203 integrally formed with the flexible substrate 1202 is led out in a direction along the substrate face of the sensor substrate 1202. On the flexible cable 1203, a conductor pattern (not shown) is formed, which constitutes a lead section connected to the conductor pattern of the electrodes Ex and Ey of the sensor formed on the sensor substrate 1202. In this instance, the sheet member 1201 and the sensor substrate 1202 have areas substantially equal to each other (though the area of the sensor substrate 1202 may be slightly smaller than that of the sheet member 1201), and the position detection sensor unit 120 is a structure substantially in the form of a rectangular plate formed of the sheet member 1201 and the sensor substrate 1202 having substantially equal areas and being adhered to each other. The flexible cable 1203 is led out from an end edge portion of the position detection sensor unit 120 in the form of a rectangular plate.
The upper face of the upper case 1101 provides a space, to which the position detection sensor unit 120 is affixed, in the form of a recessed portion 1103 of a size and a depth corresponding to the size and the thickness of the position detection sensor unit 120. A bottom portion of the recessed portion 1103 of the upper case 1101 has a form of a flat face, to which the position detection sensor unit 120 is affixed. The position detection sensor unit 120 is adhered at the sensor substrate 1202 side thereof to the bottom portion of the recessed portion 1103 by adhesive to secure the position detection sensor unit 120 to the upper face of the upper case 1101.
At an end edge position of the bottom portion of the recessed portion 1103 corresponding to the led-out position of the flexible cable 1203 of the position detection sensor unit 120, the through-hole 1104 is perforated for threading the flexible cable 1203 therethrough into the space between the upper case 1101 and the lower case 1102. The flexible cable 1203 of the position detection sensor unit 120 is bent at a substantially right angle as seen in FIG. 9B and is threaded through the through-hole 1104 into the space between the upper case 1101 and the lower case 1102 from the upper face of the upper case 1101. Since the housing 110 has a flattened shape of a small thickness, the flexible cable 1203 is again bent in the space between the upper case 1101 and the lower case 1102 and connected to the signal processing circuit 130 provided in the space between the upper case 1101 and the lower case 1102.
While, in the sectional view of FIG. 9B, a gap is illustrated between each of the sheet member 1201, the sensor substrate 1202, and the upper case 1101 to provide readily understandable illustration, in reality the members are adhered to each other by adhesive and are in a uniformly closely contacting state.